(1) Field of the Invention
The present invention relates to a technology of improving image signal resolution.
(2) Description of the Related Art
There is a trend of increasing the screen size of television sets. Generally, digital signal processes are used to increase the number of horizontal and vertical pixels for display instead of displaying original image signals supplied from broadcasting or telecommunication sources or storage media. The resolution cannot be increased simply by increasing the number of pixels based on a low-pass filter or a spline function using the sinc function.
Japanese Published Unexamined Patent Application No. 2007-324789 discloses the technology of merging multiple input image frames (hereafter just referred to as frames) into a single frame so as to increase the number of pixels while ensuring high resolution.
Japanese Published Unexamined Patent Application No. Hei 8-336046 discloses the technology of generating a weighted sum of image signals based on phase differences between three input image frames and removing aliasing components so as to ensure high resolution.
Japanese Published Unexamined Patent Application No. Hei 9-69755 discloses the technology of generating a weighted sum of image signals based on phase differences between nine input image frames and removing aliasing components so as to ensure high resolution in a two-dimensional direction including horizontal and vertical directions.